Some new designs of mobile communication devices include two or more Subscriber Identity Module (“SIM”) cards that provide users with access to multiple separate mobile telephony networks. Examples of mobile telephony networks include GSM, TD-SCDMA, CDMA2000, LTE, and WCDMA. Example multi-SIM mobile communication devices include mobile phones, laptop computers, smart phones, and other mobile communication devices that are configured to connect to multiple mobile telephony networks. A mobile communication device that includes a plurality of SIMs and connects to two or more separate mobile telephony networks using two or more separate radio-frequency (“RF”) transceivers is termed a “multi-SIM-multi-active” communication device. An example of a multi-SIM-multi-active communication device is a “dual-SIM-dual-active” communication device that includes two SIM cards/subscriptions associated with two mobile telephony networks.
When a mobile communication device includes a plurality of subscriptions, each subscription on the device may utilize a different RF resource to communicate with the subscription's associated network at any time. For example, a first subscription (e.g., a subscription to a GSM network) may use a first transceiver to transmit to a GSM base station at the same time a second subscription (e.g., a subscription to a WCDMA network) uses a second transceiver to transmit to a WCDMA base station. However, in certain frequency-band combinations of operation, the simultaneous use of the RF resources may cause one or more RF resources to desensitize or interfere with the ability of the other RF resources to operate normally because of the proximity of the antennas of the RF chains included in the multi-SIM-multi-active communication device.
Generally, receiver desensitization (sometimes referred to as “de-sense”), or degradation of receiver sensitivity, may result from noise interference of a nearby transmitter. For example, when two radios are close together with one transmitting on the uplink—sometimes referred to as the aggressor communication activity (“aggressor”)—and the other receiving on the downlink—sometimes referred to as the victim communication activity (“victim”)—signals from the aggressor's transmitter may be picked up by the victim's receiver or otherwise interfere with reception of a weaker signal (e.g., from a distant base station). As a result, the received signals may become corrupted and difficult or impossible for the victim to decode. Receiver de-sense presents a design and operational challenge for multi-radio devices, such as multi-SIM-multi-active communication devices, due to the necessary proximity of transmitter and receiver.